Cu+-Cu0 Cluster Pairs in Defective MOFs for Highly Synergistic CO2 Hydrogenation to Methanol.

Precise arrangement of multivalent Cu sites for the synchronized activation of CO2 and H2 in selective methanol synthesis remained challenging. Herein, we designed spatially arrayed Cu+-Cu0 cluster pairs confined within UiO-66 (U66) to achieve spatiotemporally directed CO2 hydrogenation to methanol. This architecture was constructed by creating missing-linker defects within U66 using L-ascorbic acid (LA), followed by sequential anchoring of high-density, adjacent Cu+-Cu0 cluster pairs (≈1:1 ratio) to yield a Cu/U66(LA-Cu) catalyst. Under reaction conditions of 220°C and 3 MPa, this catalyst achieved a methanol space-time yield of 688.1 mg·g-1·h-1 and an ultra-high methanol selectivity (97.0%). Its unity-methanol selectivity was 1.06-1.77 times that of high-stability oxide materials. Meanwhile, catalyst's stability of 200 h was significantly prolonged compared to high-selectivity MOF-based catalysts that operated stably for 60-175 h. Mechanistic studies revealed that Cu+-Cu0 cluster pairs within defective U66 not only enabled partitioned synergistic activation of CO2 and H2, but established an efficient electron/hydrogen transfer pathway. This facilitated the migration of active hydrogen species to CO2 adsorption sites, where adsorbed CO2 was converted into CO intermediates and underwent deep hydrogenation. This structural design synergistically enhanced compatibility between H2 dissociation and CO2 hydrogenation steps, enabling reaction to proceed efficiently along the RWGS + CO-hydro pathway.